1. Field of the Invention
The present invention relates to a halogen-free flameproof mesh sheet used outdoors such as a construction site for a long time.
2. Prior Art
In recent years, there has been a trend toward the construction of buildings having a large number of stories in the construction industry. Meanwhile, there has been an increase in the number of houses having a small number of stories. Flameproof mesh sheets for safety and protection and scattering prevention flameproof mesh sheets must be laid in these buildings and regulations are becoming more and more strict.
Currently, used flameproof mesh sheets and scattering prevention flameproof mesh sheets are produced by weaving yarn prepared by coating a polyester, nylon or polypropylene multi-filament fiber with a vinyl chloride-based paste resin composition and heating and then heating the obtained cloth and by coating a fabric prepared by weaving and processing a multi-filament fiber with a vinyl chloride-based paste resin composition, heating and processing to a desired shape, respectively.
A vinyl chloride containing chlorine is used as the resin composition for coating a fiber and fabric. Illustrative examples of the flame retardant include chloride-based flame retardants such as chlorinated paraffin, bromine-based flame retardants such as decabromodiphenyl oxide, and inorganic flame retardants such as antimony trioxide (Examined Japanese Patent Publication Nos. 52-41786, 53-18065 and 61-94305, Plastics, February, 1991).
In recent years, it has been globally demanded to avoid the use of resins and flame retardants containing elemental halogen which generates harmful gas at the time of combustion from the viewpoint of the environmental preservation of the earth.
Japanese Laid-open Patent Application No. 61-223045 proposes that red phosphorus and ammonium polyphosphate are kneaded into polyolefin to prevent corrosion by halogen contained in a halogen-containing compound flame retardant. However, there is unknown a flame retardant which is dispersed in an aqueous dispersion of a polyolefin resin.
In view of the above situation, it is an object of the present invention to provide a flame retardant for halogen-free flameproof mesh sheets which does not generate harmful halogen gas at the time of combustion and a flameproof mesh sheet comprising the same.
The present invention relates to:
A flame retardant for mesh sheets comprising about 1.5 to 15 parts by weight of red phosphorus and about 10 to 70 parts by weight of an ammonium polyphosphate compound based on 100 parts by weight of a solid content of an aqueous dispersion of a polyolefin resin having a resin solid content of about 20 to 45 wt %.
The polyolefin resin of the aqueous dispersion of a polyolefin resin may be selected from ethylene-methacrylic acid metal ion crosslinked copolymers and ethylene-based xcex2-olefin copolymers.
The polyolefin resin of the aqueous dispersion of a polyolefin resin may be a mixture of about 90 to 10 wt % of an ethylene-methacrylic acid metal ion crosslinked copolymer and about 10 to 90 wt % of an ethylene-based xcex1-olefin copolymer.
The red phosphorus and ammonium polyphosphate can be micro-encapsulated.
The flame retardant can further comprises about 60 to 150 parts by weight of a metal hydroxide based on 100 parts by weight of the solid content of the aqueous dispersion of a polyolefin resin. The metal hydroxide can be magnesium hydroxide and/or aluminum hydroxide.
The flameproof mesh sheet can be prepared by impregnating with the flame retardant, heating, and woven.
The flameproof mesh sheet can have an equivalent single fineness of a multi-filament fiber of about 3 to 17 denier, a total, fineness of about 1,000 to 4,500 denier, a tensile strength of about 6 to 10 g/denier and a break strength of about 14 to 45 %.
The flameproof mesh sheet can be coated by impregnating a mesh sheet fabric woven of a multi-filament fiber with the flame retardant for mesh sheets and heated.
The flameproof mesh sheet can be prepared by paralleling 1 to 4 synthetic fibers having an equivalent single fineness of about 2 to 13 denier, a total fineness of about 150 to 2,500 denier, a tensile strength of about 6 to 10 g/denier and a break strength of about 14 to 45 % and leno weaving with a weaving machine and has a mesh length of about 10 to 140 warps/10 cm and about 10 to 140 wefts/10 cm.
The flameproof mesh sheet may be used in an amount of about 60 to 350 parts by weight based on 100 parts by weight of the multi-filament fiber or the mesh sheet fabric woven of the multi-filament fiber to coat the mesh sheet fabric by impregnation.
An aqueous dispersion of a polyolefin resin is used as a base material in the present invention because a multi-filament fiber and fabric are fully impregnated with a flame retardant and uniformly coated with the flame retardant.
Preferable, the aqueous dispersion of a polyolefin resin comprises as the polyolefin resin an ethylene-methacrylic acid metal ion crosslinked copolymer containing about 10 to 20 wt % of methacrylic acid and can have a solid content of about 20 to 45 wt %, a particle diameter of about 0.01 to 3 xcexcm, a pH of 8 to 11, a viscosity of about 30 to 1,000 cp (a BM type viscometer, 6 rotations). The polyolefin resin is particularly preferably an ethylene-methacrylic acid metal ion crosslinked copolymer and can have a resin surface hardness of about D-40 to 75 (Shore-D: ASTMD2240) such as an ionomer resin exemplified by S-300, S-650 or S-100 (of Mitsui Petrochemical Industry Co.).
An ethylene-based xcex1-olefin copolymer may be used and a dispersion thereof has a solid content of about 20 to 45 wt %, a particle diameter of about 1 to 10 xcexcm, a pH of about 8 to 11, a viscosity of about 2,000 to 8,000 cp (a BM type viscometer, 6 rotations) and a resin surface hardness of about A-80 to 97 (Shore A: ASTMD). The ethylene-based xcex1-olefin copolymer is preferably a thermoplastic elastomer resin comprising about 50 wt % or more of ethylene, such as A-100 or A-200 (of Mitsui Petrochemical Industry Co.).
When a mixture of about 90 to 10 wt % of an ethylene-methacrylic acid metal ion crosslinked copolymer and about 10 to 90 wt % of an ethylene-based xcex1-olefin copolymer is used, the surface hardness of the ethylene-methacrylic acid metal ion crosslinked copolymer having a higher surface hardness and the surface hardness of the ethylene-based xcex1-olefin copolymer having a lower surface hardness are well balanced and the feeling of a conventional flameproof mesh sheet produced from a soft vinyl chloride resin is obtained. As for the preferable ratio of the two materials, the ethylene-methacrylic acid metal ion crosslinked copolymer may be used in a proportion of about 80 to 40 wt % and the ethylene-based xcex1-olefin in copolymer in a proportion of about 20 to 60 wt %.
Red phosphorus used in the present invention may be preferably micro-encapsulated. Use of the micro-encapsulated red phosphorus makes it possible to reduce an increase in the viscosity of an aqueous dispersion when red phosphorus is mixed into the olefin aqueous dispersion. Further, the flameproof mesh sheet is detached and washed to remove dirt after it is spread at a construction site and used for 4 to 8 months. It is washed by immersing it in hot water heated at about 40xc2x0 C. and containing a detergent for several hours. At this point, red phosphorus can be prevented from dissolving in water by micro-encapsulation. The concentration of red phosphorus is about 75 to 95 % and the average particle diameter thereof is about 10 to 40 xcexcm.
Micro-encapsulation can be suitably carried out by coating the surface of a red phosphorus particle with a resin or inorganic material by interfacial polymerization, coacervation or the like.
The ammonium polyphosphate compound used in the present invention may be ammonium polyphosphate or amide polyphosphate. Use of the micro-encapsulated ammonium polyphosphate compound makes it possible to reduce an increase in the viscosity of the aqueous dispersion when the ammonium polyphosphate compound is mixed into the aqueous dispersion of an olefin resin. Further, the flameproof mesh sheet is detached and washed to remove dirt after it is spread at a construction site and used for about 4 to 8 months. It is washed by immersing in hot water heated at about 40xc2x0 C. and containing a detergent. At this point, the ammonium polyphosphate compound can be made hardly soluble in water and stable by micro-encapsulation. The concentration of phosphor contained in the ammonium polyphosphate compound is about 15 to 35 % and the average particle diameter of the compound is about 5 to 40 xcexcm. Micro-encapsulation can be carried out like red phosphorus.
Red phosphorus and an ammonium polyphosphate compound may be used as flame retardants in the present invention because when a resin composition containing red phosphorus is brought close to flames, the resin and red phosphorus on the surface first burn and the resin is bonded to oxygen in the air to become carbon dioxide gas, water and carbon. In this case, red phosphorus promotes the carbonization of the ethylene-methacrylic acid metal ion crosslinked copolymer and the ethylene-xcex1-olefin copolymer. Meanwhile, red phosphorus is bonded to oxygen to become an oxide which is further bonded to water to become condensation phosphoric acid. A film made from a mixture of carbon and condensation phosphoric acid formed on the surface of the resin becomes an oxygen impermeable layer on the surface of the resin, suppresses the combustion of the resin and makes the resin flame resistant.
Red phosphorus may exist in an amount of 1.5 to 15 parts by weight based on 100 parts by weight of the polyolefin resin solid content of the aqueous dispersion of a polyolefin resin having a solid content of 20 to 45 wt %. If the content of red phosphorus is less than 1.5 parts by weight based on the resin solid content, its flameproofing effect may not be provided and if the content is more than about 15 parts by weight, its flameproofing effect will not be improved, the resulting flameproof mesh sheet will have a strong red tint and difficult to be colored even with a pigment.
In this case, when an ammonium phosphate compound is present, the ammonium polyphosphate compound thermally decomposes at the time of combustion and generates nitrogen gas which shuts off oxygen. The ammonium polyphosphate compound promotes the carbonization of a polyolefin resin as a dehydrocarbonizing agent and improves a combustion effect while it generates nitrogen-containing gas. In the present invention, the ammonium polyphosphate compound must be existent in an amount of about 10 to 70 parts by weight based on 100 parts by weight of the polyolefin resin solid content of the aqueous dispersion of a polyolefin resin having a solid content of about 20 to 45 wt %. Below 10 parts by weight, a flameproofing effect may not be provided and above 70 parts by weight, a flameproofing effect may not be improved.
Nova Excel 140 or Nova Red 120 (Rin Kagaku Kogyo Co.) may be used as red phosphorus.
TERRAJU-60 or TERRJU-70 (of Chisso Corp.), or Hostafuram AP462 (Hoechst Co.) may be used as the ammonium polyphosphate compound.
When a metal hydroxide is further used, a great flameproof effect may be obtained advantageously. The metal hydroxide is preferably magnesium hydroxide and/or aluminum hydroxide which can be used in conjunction with red phosphorus and ammonium polyphosphate to obtain a greater effect. The metal hydroxide can be existent in an amount of about 60 to 150 parts by weight based on 100 parts by weight of the polyolefin resin solid content of a polyolefin resin aqueous dispersion.
When the amount of the metal hydroxide is less than 60 parts by weight, its effect of promoting flame resistance can be small and when the amount is more than about 150 parts by weight, the viscosity of the aqueous dispersion of a polyolefin resin can increase disadvantageously.
As the aluminum hydroxide may be used: Hijilite H-42M or Hijilite H-43M (Showa Denko K.K.).
As the magnesium hydroxide may be used: Kisuma 5 (Kyowa Kagaku Kogyo Co.).
The multi-filament used in the present invention is at least one multi-filament selected from polyesters, nylons, polypropylene and vinylon. It is preferably a polyester fiber from viewpoints of strength and thermal shrinkage.
A high-strength and lightweight flameproof mesh sheet can be obtained by controlling the tensile strength of the multi-filament fiber to about 6 to 10 g/denier. A flameproof mesh sheet having high toughness and high impact energy absorption at the time of falling can be obtained by controlling the break elongation of the multi-filament fiber to about 14 to 45 %.
The multi-filament which is treated with a flame retardant and then woven has an equivalent single fineness of about 3 to 17 denier, preferably about 3 to 12 denier, particularly preferably 4 to 9 denier and a total fineness of about 1,000 to 4,500 denier, preferably about 1,260 to 3,500 denier, particularly preferably about 1,500 to 3,000 denier.
The multi-filament used in a fabric which is woven and then treated with a flame retardant has an equivalent single fineness of about 2 to 13 denier, preferably about 2 to 11 denier, particularly preferably about 2.5 to 9 denier and a total fineness of about 150 to 2,500 denier, preferably about 200 to 2,000 denier, particularly preferably about 250 to 1,500 denier. By controlling tensile strength to 6 to 10 g/denier, a high-strength and lightweight flameproof mesh sheet can be obtained and by controlling break elongation to about 14 to 45 %, a flameproof mesh sheet having high toughness and high impact energy absorption at the time of falling can be obtained.
A flameproof mesh sheet which needs to have high strength and toughness is prepared by paralleling 1 or 2 to 4 filament fibers and leno weaving them with a Dobby weaving machine. A scattering prevention flameproof mesh sheet is prepared by leno weaving a fabric of a single filament fiber with a weaving machine in most cases. A flameproof mesh sheet prepared in this manner can have a mesh length of about 10 to 140 warps/10 cm and about 10 to 140 wefts/10 cm, preferably 20-120 to 140 warps/10 cm and about 20 to 120 wefts/10 cm.
As for the weight ratio of the multi-filament fiber and fabric to the solid content of a flame retardant, the solid content of the flame retardant is used in an amount of about 60 to 350 parts by weight based on 100 parts by weight of the multi-filament fiber and fabric. When the solid content of the flame retardant is less than about 60 parts by weight based on 100 parts by weight of the multi-filament fiber or fabric, coating becomes nonuniform and the multi-filament fiber and fabric are partly exposed, thereby deteriorating outer appearance and weatherability. Further, flame resistance also lowers. When the solid content is more than about 350 parts by weight, the weight of the flameproof mesh sheet may increase with the result of deteriorated handling properties disadvantageously.
A pigment, dye, ultraviolet absorber, optical stabilizer, antioxidant, stabilizer, diluent, thickening agent, foaming agent, mold preventing agent, alga preventing agent and the like can be used in conjunction with the flame retardant in the present invention by suitably selecting types and amounts thereof.
A description is subsequently given of a process for producing a flameproof mesh sheet of the present invention. When the flameproof mesh sheet of the present invention is produced using a multi-filament fiber, coated yarn prepared by coating the fiber with a flame retardant through a sizing nozzle, heating and gelling is taken up by a winder. This coated yarn taken up by the winder is woven into a fabric by a weaving machine. This fabric is introduced into a heating furnace and heated for non-shifting processing in order to obtain cloth.
This cloth is cut to a predetermined size, sewed and subjected to non-shift processing to obtain a halogen-free flameproof mesh sheet.
When the flameproof mesh sheet of the present invention is produced using a fabric, woven cloth may be obtained by weaving the multi-filament fiber by a Dobby weaving machine. After this woven cloth is immersed in a tank filled with a flame retardant for mesh sheets and let pass through the tank, it is dried with an air blow, introduced into a heating furnace and gelled by heating to obtain coated cloth. To increase the amount of the flame retardant coated on the fabric, the fabric is immersed in and let pass through the tank filled with the flame retardant at least two times to produce coated cloth. The cloth is cut to a predetermined size, sewed and subjected to non-shifting processing to produce a halogen-free flameproof mesh sheet.